This invention relates to exercise apparatus, and particularly to apparatus which simulates stair climbing.
In such apparatus, the user's energy is exerted in repeatedly lifting the user's body by shifting weight alternatively from one pedal to another. Each of two pedals moves between an upper position and a lower position. As one foot of the user presses down on the first pedal in its upper position, that pedal is driven down by the weight of the user, working against a resistance. The exercise apparatus then brings the second pedal to its upper position; and the user presses down on the second pedal with the other foot, raising the user's weight, and driving the second pedal down. The arrangement is such that a single resistance device provides the resistance for both pedals as they are separately urged downwardly.
An example of a stair climbing exercise apparatus is shown in Potts U.S. Pat. No. 4,708,338. In that patent, each pedal is moved up and down, as it travels along an arc at the end of a pivoted arm. Resistance is provided by a dynamic brake (alternator), combined with a transmission which converts the pedal motion to a much faster speed at the alternator. Each pedal is connected to the transmission by a one-way clutch which transfers force from each pedal arm to the transmission in only one direction of motion (the downward motion of the pedal). In the other direction of pedal motion, force is not transmitted between the pedal and the dynamic brake; and the pedal is returned to its upper position by a spring.
Two significant deficiencies of the stair climber just described are its high cost, and its limited speed range. The range limitation results from the inherent limitations of a transmission (gear box) driving the dynamic brake.